The present invention relates to an optical head for an information recording/reading apparatus, in which high density information can be recorded and read by making use of an optical interaction in a minute area on a medium to read structural or optical information formed on the minute area or record such information on the minute area.
The development of information recording/reading apparatus using light is evolving toward the direction of larger capacity and smaller size, and thus a higher density of recording bits has been demanded. As a measure for achieving that, techniques using a violet semiconductor laser or SIL (solid immersion lens) have been under study. However, in those techniques, the improvement of recording density can be expected to be only several times that of the existing recording denisty, because of the problem of diffraction limit of light. Instead of that, as a technique that handles the optical information of such minute area beyond the diffraction limit of light, an information recording/reading method making use of a near-field light is expected.
This method makes use of a near-field light, which is generated by an interaction between a minute area and an optical aperture having a size smaller than the wavelength of light. This method enables the handling of optical information in an area having a size less than the wavelength of light, which would be beyond a limit of the conventional optical system. Replaying of the optical information is performed by converting a great amount of near-field light, which localizes on the surface of the recording medium by irradiating a scattering light, and is converted into a bound ray by the interaction with a minute aperture (collection mode), and reading the data stored on the minute area on the medium. Furthermore, it is also possible to read by irradiating the near-field light generated form a minute aperture on a surface of a medium, and detecting the scattered light converted by the intersection with minute unevenness on the surface of the medium, on which the information has been recorded, with a detector provided separately (illumination mode). Recording is performed by irradiating a near-field light generated from a minute aperture on a surface of the recording medium to vary the configuration of a minute area on a medium (heat mode recording), or to vary a refractive index or transmittance of the minute area (photon mode recording). By using such a head having an optical minute aperture, which is sized less than the diffraction limit of light, the high density optical information recording/reading apparatus, in which the density of recording bits exceeds that of the conventional optical information recording/reading apparatus, can be realized.
The structure of the recording/reading apparatus making use of a near-field light is almost the same as that of magnetic disc apparatus, except that a near-field light head is used instead of a magnetic head. A slider attached to the distal end of a suspension arm and provided with an optical minute aperture optical is kept floating at a certain height by the flying-head technology, and a desired data mark existing on a disc is accessed. In order to make the near-field light head follow the high speed revolution of the disc, a flexible-posture function is provided for stabilizing the posture of the slider with respect to the undulation of the disc. In such a structure of a near-field light head, as the method of feeding light to the slider, means for connecting optical fibers or an optical waveguide to the slider or arm, or means for irradiating a beam of laser, which is disposed horizontally to the slider or above the slider, directly on the slider has been employed.
However, when a light is incident on such a structure, since a structural body such as optical fibers or an optical waveguide is connected between the slider and the arm, it becomes an obstacle to the free motion of the slider, and causes the posture control of the slider with respect to the motion of disc to be difficult and the distance between the disc and the slider cannot be kept constant. As a result, the SN ratio of the output from the optical information written on the disc is deteriorated, and there have been difficulties in writing and reading signals. Furthermore, when the signal is incident on the slider directly from a laser disposed above the slider, from the necessity of synchronizing the incident light with the raped motion of the slider, it is required to provide an additional structural body, which can follow the motion of the slider, and it has been extremely difficult. Moreover, by providing such an additional structural body, the apparatus itself becomes larger in size, and it has made the recording/reading apparatus more difficult to be miniaturized.
In order to solve the above-described problems, an optical head for recording and reading information is provided which is comprised of a slider that receives a buoyant force by means of relative motion with respect to a medium a, minute structure formed on the slider, in a surface facing the medium, for at least one of generating or detecting a near-field light, an in-slider optical waveguide mechanism formed on the slider and connected optically to the minute structure, an arm for holding the slider and applying a loading force to the slider; an in-arm optical waveguide mechansim formed on the arm for guiding a light to the in-slider optical waveguide mechanism, and an optical waveguide mechanism that contacts the in-arm optical waveguide mechansim and contacts the in-slider optical waveguide mechanism and contacts the in-slider optical waveguide mechanism, wherein a loading force is applied to the slider through the optical waveguide mechanism.
Furthermore, it is characterized in that the optical waveguide mechanism and the in-arm optical waveguide mechanism are formed in one united body.
Furthermore, it is characterized in that the optical waveguide mechanism and the in-slider optical waveguide mechanism are formed in one united body.
Furthermore, it is characterized in that an area where the optical waveguide mechanism contacts the in-arm optical waveguide mechanism or an area where the optical waveguide mechanism contacts the in-slider optical waveguide mechanism or both areas of those are extremely small.
Still furthermore, it is characterized in that the optical waveguide mechanism contacts the in-arm optical waveguide mechanism or the in-slider optical waveguide mechanism or both of those, at one point.
According to the present invention, it is possible that the light from the arm side is transmitted to the slider with certainty and, at the same time, the obstacle to the free motion of the slider, which would be caused by the structural body that guides a light to the slider, is eliminated, and the posture of the slider is controlled freely in response to the motion of the medium, while keeping the distance between the medium and the slider scanning on the medium constant. As a result, signals can be input and output with a high SN ratio and stability. Moreover, since the optical waveguide mechanism that transmits a light and the slider are minute structural bodies, which are produced by a micro-machining process using silicon or the like, the suspension function of the arm is not obstructed and the overweight nature of the slider has no influence on its motion. Accordingly, the entire apparatus can be miniaturized. Moreover, since the entire optical head or at least a great portion thereof is produced by a mass production line with semiconductor processes, its cost can be made lower.
Furthermore, an optical head is characterized in that the optical waveguide mechanism has a part shaped like a cone or a hanging bell having a pointed top, and contacts at the part.
Furthermore, it is characterized in that the optical waveguide mechanism has a part shaped as a part of spherical surface and contacts at the part.
Furthermore, it is characterized in that the optical waveguide mechanism has a part having a condensing function.
By making the optical design of the optical waveguide according to the present invention, it is possible that a light is transmitted to the slider with certainty and a large amount of light is supplied to the slider. Furthermore, by adjusting the spherical shape, the conical shape or the refractive index of the optical waveguide, it is possible to collect more light around a minute aperture formed in the slider for generating a near-field light. As the result, signals can be input and output with a high SN ratio, and an apparatus having a high reliability can be produced.
Moreover, an optical head is characterized in that the loading force is applied toward the center of gravity of the slider, and the minute structure that exists in a surface facing the medium is positioned on a straight line, which links the point the slider receives the loading force with the center of gravity.
Furthermore, it is characterized in that the minute structure is positioned in the vicinity of an edge of a surface facing the medium, depending on the shape of the slider or its density distribution or the combination of those.
Furthermore, it is characterized in that there exists a recess having a size corresponding to ⅕ or more of the volume of the slider, at a portion in a surface opposite to the surface facing the medium of the slider.
Furthermore, it is characterized in that there exists a difference in thickness having a differential level corresponding to {fraction (1/10)} or more of the averaged thickness of the slider, in a surface facing the medium of the slider.
Still furthermore, it is characterized in that a material having a density different from that of the slider occupies {fraction (1/10)} or more of the total volume of the slider.
According to the present invention, although the posture of the floating slider inclines slightly with respect to the medium surface, due to an air pressure distribution that the surface facing the medium of the slider receives by the high speed motion of the medium, the aperture can be disposed at a region close to the medium in the surface facing the medium of the slider, and thereby further more minute recording and reading becomes possible. Moreover, by bringing the aperture closer to the medium, SN ratio in recording and reading can be improved, and an information recording/reading apparatus having high stability and reliability can be produced. Furthermore, resulting from the improved SN ratio, a high-speed recording/reading becomes possible without a necessity of the large-powered light source, and thereby a small-sized, thin type and low-priced information recording/reading apparatus can be produced.